Diabetes refers to a disease state or process derived from multiple causative factors and is characterized by elevated levels of plasma glucose (hyperglycemia) in the fasting state or after administration of glucose during a glucose tolerance test. Persistent or uncontrolled hyperglycemia is associated with a wide range of pathologies. Diabetes mellitus, is associated with elevated fasting blood glucose levels and increased and premature cardiovascular disease and premature mortality. It is also related directly and indirectly to various metabolic conditions, including alterations of lipid, lipoprotein, apolipoprotein metabolism and other metabolic and hemodynamic diseases. As such, the diabetic patient is at increased risk of macrovascular and microvascular complications. Such complications can lead to diseases and conditions such as coronary heart disease, stroke, peripheral vascular disease, hypertension, nephropathy, neuropathy, and retinopathy. Accordingly, therapeutic control and correction of glucose homeostasis is regarded as important in the clinical management and treatment of diabetes mellitus.
There are two generally recognized forms of diabetes. In Type 1 diabetes, or insulin-dependent diabetes mellitus (IDDM), the diabetic patient's pancreas is incapable of producing adequate amounts of insulin, the hormone which regulates glucose uptake and utilization by cells. In Type 2 diabetes, or noninsulin dependent diabetes mellitus (NIDDM), patients often produce plasma insulin levels comparable to those of nondiabetic subjects; however, the cells of patients suffering from type 2 diabetes develop a resistance to the effect of insulin, even in normal or elevated plasma levels, on glucose and lipid metabolism, especially in the main insulin-sensitive tissues (muscle, liver and adipose tissue).
Insulin resistance is not associated with a diminished number of cellular insulin receptors but rather with a post-insulin receptor binding defect that is not well understood. This cellular resistance to insulin results in insufficient insulin activation of cellular glucose uptake, oxidation, and storage in muscle, and inadequate insulin repression of lipolysis in adipose tissue, and of glucose production and secretion in the liver. A net effect of decreased sensitivity to insulin is high levels of insulin circulating in the blood without appropriate reduction in plasma glucose (hyperglycemia). Hyperinsulinemia is a risk factor for developing hypertension and may also contribute to vascular disease.
Patients who have insulin resistance often have several symptoms that together are referred to as Syndrome X, or the metabolic syndrome. According to one widely used definition, a patient having metabolic syndrome is characterized as having three or more symptoms selected from the group of five symptoms: (1) abdominal obesity; (2) hypertriglyceridemia; (3) low high-density lipoprotein cholesterol (HDL); (4) high blood pressure; and (5) elevated fasting glucose, which may be in the range characteristic of Type 2 diabetes if the patient is also diabetic. Each of these symptoms is defined clinically in the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III or ATP III), National Institutes of Heath, 2001, NIH Publication No. 01-3670. Patients with metabolic syndrome, whether or not they have increase risk of developing the macrovascular and microvascular complications that occur with Type 2 diabetes, such as atherosclerosis and coronary heart disease.
The available treatments for Type 2 diabetes, some of which have not changed substantially in many years, are used alone and in combination. Many of these treatments have recognized limitations, however. For example, while physical exercise and reductions in dietary intake of fat, high glycemic carbohydrates, and calories can dramatically improve the diabetic condition, compliance with this treatment is very poor because of well-entrenched sedentary lifestyles and excess food consumption, especially of foods containing high amounts of saturated fat. Increasing the plasma level of insulin by administration of sulfonylureas (e.g. tolbutamide and glipizide) or meglitinide, which stimulate the pancreatic beta-cells to secrete more insulin, and/or by injection of insulin when sulfonylureas or meglitinide become ineffective, can result in insulin concentrations high enough to stimulate insulin-resistance in tissues. However, dangerously low levels of plasma glucose can result from administration of insulin or insulin secretagogues (sulfonylureas or meglitinide), and an increased level of insulin resistance due to the even higher plasma insulin levels can occur. The biguanides are a separate class of agents that can increase insulin sensitivity and bring about some degree of correction of hyperglycemia. These agents, however, can induce lactic acidosis, nausea and diarrhea.
The glitazones (i.e. 5-benzylthiazolidine-2,4-diones) are another class of compounds that have proven useful for the treatment of Type 2 diabetes. These agents increase insulin sensitivity in muscle, liver and adipose tissue in several animal models of type 2 diabetes, resulting in partial or complete correction of the elevated plasma levels of glucose without occurrence of hypoglycemia. The glitazones that are currently marketed are agonists of the peroxisome proliferator activated receptor (PPAR), primarily the PPAR-γ subtype. PPAR-γ agonism is generally believed to be responsible for the improved insulin sensititization that is observed with the glitazones. Newer PPAR agonists that are being tested for treatment of Type 2 diabetes are agonists of the alpha, gamma or delta subtype, or a combination thereof, and in many cases are chemically different from the glitazones (i.e., they are not thiazolidinediones). Serious side effects (e.g. liver toxicity) have been noted in some patients treated with glitazone drugs, such as troglitazone.
Compounds that are inhibitors of the dipeptidyl peptidase-IV (DPP-IV) enzyme are also under investigation as drugs that may be useful in the treatment of diabetes, and particularly Type 2 diabetes.
Additional methods of treating hyperglycemia and diabetes are currently under investigation. New biochemical approaches include treatment with alpha-glucosidase inhibitors (e.g. acarbose), protein tyrosine phosphatase-1B (PTP-1B) inhibitors, and glucagon receptor antagonists.
The free fatty acid receptor GPR40 (FFAR or FFAR1) is part of a family of recently deorphanized GPCR's that bind fatty acids of varying chain lengths. GPR40 binds long-chain FFA, particularly oleate, as well as the PPAR-gamma agonist rosiglitazone. GPR40 is highly expressed in the pancreas, where it functions to produce insulin release upon agonist stimulation through activation of the PKC pathway resulting in Ca++ efflux. The receptor is also expressed in throughout the brain in monkeys and humans, but not in rodents.
Initial studies in GPR40 KO mice reported that they were resistant to high-fat diet-induced insulin resistance, suggesting an antagonist mechanism would be appropriate for this target. However, given the localization and function of the receptor, as well as the fact that most groups have not replicated this initial finding, the use of an agonist appears to be the appropriate answer for increasing insulin release for the treatment of diabetes. In facts, it has been demonstrated that agonists of GPR40 stimulate glucose-dependent insulin secretion in vitro and lower an elevated blood glucose level in vivo. See for example, Diabetes 2008, 57, 2211; J. Med. Chem. 2007, 50, 2807.
Compounds that act as GPR40 receptor agonists are known in the art. WO2008/054674 (assigned to Merck) discloses bicyclic derivatives of the formula
These derivatives are said to be useful in treating Type 2 diabetes mellitus and conditions associated with the disease, including insulin resistance, obesity and lipid disorders. WO2006/083781, WO2006/083612, US 2007/0265332 and WO2008/054674 (all assigned to Merck) disclose bicyclic derivatives that modulate the GPR40 receptor and are said to treat Type-2 diabetes. For example, WO2006/083612 discloses compounds of the formula
where R1 is optionally substituted cyclic group such as pyridine, pyrazine, pyrimidine, etc.
Other bicyclic derivatives are known in the art to be useful in treating disease states such as diabetes, obesity and metabolic disorder. WO 2004/058174 (assigned to Bayer) discloses indane acetic acid derivatives of the formula
and states that these derivatives are useful in treating Type-2 diabetes, obesity and atherosclerotic diseases.
US 2005/0245529 (Boehringer Ingelheim) discloses alkyne derivatives that are said to be useful in treating metabolic disorders and diabetes by antagonizing the MCH-receptor.
There is a need for new compounds, formulations, treatments and therapies to treat diseases and disorders associated with the GPR40 receptor that exhibit good safety profiles and efficacy by controlling insulin levels in a mammal. It is, therefore, an object of this invention to provide compounds that are useful in the treatment or prevention or amelioration of diseases and disorders associated with the GPR40 receptor, such as hyperglycemia, diabetes, and related metabolic diseases and indications.